Peristaltic pumps are devices that transfer fluid through one or more elongate, at least partially flexible, tube(s) by compressing each tube in a peristaltic manner. Fluid transport through the tube is effectuated by moving a region of compression along the length of the tube. Such movement of the region of compression is typically achieved by way of one or more rollers or reciprocating pushers that progressively move an area of compression along the length of the tubing to thereby pump fluid through the tubing in a peristaltic motion. Such pumps are often used in medical applications including intravenous or subcutaneous infusion, withdrawal of fluids as in wound drainage systems as well as various laboratory instruments and industrial applications, such as industrial applications where toxic or corrosive fluids are pumped.
Typical linear peristaltic pumps include those described in U.S. Pat. No. 2,877,714 (Sorg et al.), U.S. Pat. No. 4,671,792 (Borsannyi), U.S. Pat. No. 4,893,991 (Hemingway et al.) and U.S. Pat. No. 4,728,265 (Canon), the entire disclosures of which are expressly incorporated herein by reference. In general, these pumps require a drive shaft that is parallel to a resilient tube and a plurality of cams along the drive shaft to move pushers toward and away from the tube.
Rotary peristaltic pumps generally dispose a resilient tube along a circular path, with a number of rollers mounted around the circumference of a circular rotor-sequentially rolling along the tube to occlude the tube and force liquid through the tube. Typical of such pumps are those disclosed in U.S. Pat. No. 4,886,431 (Soderquist et al.) and U.S. Pat. No. 3,172,367 (King), the entire disclosures of which are expressly incorporated herein by reference. These pumps often have relatively low efficiency and impose high shear and tension stresses on the tube causing internal tube wall erosion or spallation. The tube may eventually be permanently deformed so that the tube becomes flattened into a more oval shape and carries less liquid.
The prior art has also included another type of peristaltic pump wherein a tube is arranged along a circular path and a cylindrical cam that rotates eccentrically is used to sequentially move a plurality of blunt pushers or fingers to sequentially compress regions of the tube from one end of the path to another and of the path. Examples of such pumps are described in German Patent No. 2,152,352 (Goner) and Italian Patent No. 582,797 (Tubospir), the entire disclosures of which are expressly incorporated herein by reference. In general, these “finger” type peristaltic pumps tend to be less complex than linear peristaltic pumps. However, the pressure exerted by the blunt fingers on the tubing can reduce the useable life of the tubing and can, in at least some cases, cause internal tube wall erosion or spallation resulting in possible loss of particulate matter from the tube wall into the fluid stream. Also, in at least some cases, tubes with different wall thicknesses may not be accommodated by these pumps, since with thinner than standard tubes the fingers will not properly occlude the tube and with thicker than standard tubes the tube will close prematurely and be subject to excessive compression, requiring higher cam drive power and causing excessive wear on the cam and tube.
In many applications of peristaltic pumps, in particular medical applications, it is important to promptly detect when the pump ceases to operate due to an occlusion in the pump tube either before or after the pump. In other applications, it is equally important to monitor the pressure in the tubing. An input occlusion occurring in the tube leading to the pump will cause the tube to collapse due to the fluid being sucked from the input side and pushed out the output side. An output occlusion occurring in the tube leading away from the pump will continue to push liquid into the output tube, inflating the tube and possibly causing it to burst. In either case, fluid flow to the end use is stopped or reduced.
One type of peristaltic pump that is especially effective is the curvilinear peristaltic pump described in U.S. Pat. No. 5,791,881 (Moubayed et al.), the entire disclosure of which is incorporated herein by reference. In the pump described in U.S. Pat. No. 5,791,881, a resilient tube is disposed against a generally circular platen and a rotating cam member sequentially and radially moves a plurality of fingers such that the fingers compress the tube and force the fluid through the tube in a peristaltic fashion. In this curvilinear peristaltic pump of the prior art, the cam drives the pump fingers in a radial direction. Because the pump fingers extend in a radial direction from the curved cam surface, the pump must be large enough (in the radial direction) to accommodate the outer radial length of the cam, the height of the pump fingers and the thickness of the concave curved platen.
There remains a need in the art for the development of new peristaltic pumps that provide advantages and/or useful improvements or differences over those of the prior art.